Active-matrix organic light-emitting diode (AMOLED) display devices have advantages such as a light and thin design, active light emission, a wide viewing angle, and a fast response speed, and are new display devices that have broad development prospects. However, due to manufacture procedures, materials, and the like, uniformity of brightness of the OLED display devices is poor, and this has always been a big problem that affects development of AMOLED display devices.
FIG. 1 is a schematic structural diagram of an AMOLED pixel drive circuit in the prior art. The drive circuit has a 2T1C structure. T1 is a switching transistor, T2 is a drive transistor, Cst is a gray-scale storage capacitor, and an OLED is an organic light-emitting diode. When a scanning line G outputs a scanning signal, and the transistor T1 is turned on, a gray-scale data signal Vdata charges the gray-scale storage capacitor Cst through the transistor T1. When the gray-scale storage capacitor Cst is charged to a predetermined value, the transistor T2 is turned on, and a drive signal ELVDD lightens the OLED through the transistor T2.
A current formula of the OLED in the AMOLED is shown as follows:
            I      oled        =                  1        2            ⁢              μ        n            ⁢              C        ox            ⁢              W        L            ⁢                        (                                    V              sg                        -                          V              th                                )                2              ,wherein μn represents carrier (electron) mobility ratio (cm2/V·s); cox represents gate oxide unit-area capacitance (F/cm2);
  W  Lrepresents a width-length ratio of the drive transistor; Vsg represents a voltage difference between a source S and a gate G of the drive transistor; and Vth represents a threshold voltage (V) of the drive transistor, and an absolute value is taken.
According to the formula, it can be seen that, a threshold voltage Vth of the transistor T2 has an obvious effect on current of the OLED. In order to improve uniformity of brightness of a panel, the threshold voltage Vth of the transistor T2 needs to be compensated.